In the category of airborne contaminants, viruses and bacteria are the most prevalent and potentially dangerous. Viruses range in size from about 20 to about 250 nanometers. Some of the most infectious viruses include the human flu virus, the avian flu virus (bird flu), rhinitis (the common cold) and SARS (severe acute respiratory syndrome). In many instances, human contact with viruses results in severe illness and sometimes, death. Bacteria, on the other hand, average about 1000 nanometers. Harmful bacteria include anthrax, which is a potential agent in biological warfare. Airborne particles such as pollen are common causes of allergic reactions such as hay fever.
A filter membrane is needed which has a controlled porosity in the low nanometer range, is amenable to any geometrical shape and can be used as a face mask or building filter, for example, for potentially biologically-infectious agents and pollutants.